Method of grinding threader work



1927. Jan 11, J. BATH METHOD OF GRINDING THREADED WORK Original Filed Jan. 1922 fizz/87%?" (737/372 BCLZ'7Z m Patented Jan; 11, 1927.

' UNITED STATES 1,614,225 PATENT OFFICE.

JOHN BATH, OF WOB GESTER, MASSACHUSETTS.

METHOD OF GRINDING THREADED WORK.

Original application filed January 9,-1922, Serial No. 527,812. Divided and this application filed Kay 12. 1923. Serial No. 638,686..

This invention is a division of my prior application Serial No. 527,812, filed Jan. 9; 1922, and relates particularly to the production of ground screw threads by an improved method or process.

It is the object of in present invention to provide an improve method by which ground screw threads or other threaded work may be manufactured at an economilocal production rate while at the same time carefully preserving the original hardness of the tempered steel and producing the highest grade of finish.

More specifically, my improved process involvesa rapid alternation of grinding and cooling operations together with the application of lubricant to the work in a particularly'etlective manner by which all dust andwaste is removed from the out.

One type ofimechanism for carrying out my improved method or process is shown in the drawings, in which- Fig. 1 is a partial sideelevation of my improved grinding wheel and the device for supplying lubricant thereto, thework being shown in section;

Fi' 2 is an edge View of the grinding wheeT, partly in section; and

Fig. 3 is a sectional plan view taken along the line 33 in Fig. 1.

Referring to the drawings, I have shown the threaded work in the form of a tap T of a usual type positioned adjacent a grinding wheel 10. It will be understood that the tap is mounted upon centers to rotate at a comparatively slow speed about its axis in the direction of the arrow a in Fig. 1.

The grindingwheel 10 rotates in the direc tion of the arrow 6 in Fig. 1 at a comparatively high speed. The cutting edge of the grinding wheel 10 is preferably formed substantiallyas shown in section in Fig. 2, the extreme outer or cutting portion 11 being shaped to correspond to the particular type 1 threaded work from high speed steel isa.

of thread to be ground and projecting 0ut-' ward from the body of the wheel, as indicated. The cutting ortion 11 is also preferably provided with straight parallel side portions 12 for a purpose to be described.

A very important feature of my invention consists in providing openings or recesses 13 in the edge portion 11 ofthe wheel. These openings are of substantial length and, as shown in the drawings, each opening t is between one third and onehalf of the length of theadjacent edge portion of the wheel. It will be understood that these proportions may be varied within rather wide limits. 1

In the preferred form of my tap grinding mechanism, I also provide a pipe 15 b which lubricant isforcibly supplied to the grinding 'wheel and to the work being ground. The lower endv of the pipe 15 on the side adjacent the wheel 10 is provided with a slot or opening 16. The pipe is positioned so that the cutting edge 11 of the wheel will'project through the slot l6 into the interiorof the pipe 15 and directly into the stream of oil or other lubricant which is forced through the ipe. The strai ht side portions 12 of the w eel ermit the ct ge portion 11 to project further mto the pipe 15 than would be otherwise possible, and the pipe protects the edge of the wheel from injury. It is also possible to adjust the pipe relatively to the wheel or work with much less probability ofstriking the edge of the wheel.

In the operation of my improved mechanism, as previously stated, the work is rotated in the direction of the arrow a and the wheel in the direction of the arrow b. The preferred speed of rotation of the wheel is such that it revolves about four times while passing one toothed portion or land of the tap.

The wheel 10, as shown in the drawings, will have about twentyfive openings 13 around its circumference and consequently about one hundred short cutting'sections of the grinding wheel edge will engage each toothed portion of the tap.

Severa important advantages arise from the provision of the openings in the grinding wheel edge, particularly when associated with my improved device'for conveying lubricant thereto. j

The manufactureof ground taps and other comparatively recent development in the art the wheel remains in close grinding contact with the teeth for the entire period required for grinding each tooth. The grinding operation necessarily generates heat and this continuous contact causes the generated heat to have an accumulative effect on'the thread.

t is found by inspection and test that teeth thus ground become softer toward the rear end of each tooth portion, the temperature of the teeth being gradually raised as the grinding operation continues. This softening of the metal commonly occurs only inthe extreme outer surface or skin of the work, but is nevertheless sufficient to seriously impair the cutting qualitiesthereof.

With my improved grinding wheel, particularly when associated with my improved lubricating device, I am able to grind the teeth or threads without raising the temperature thereof sufiiciently to effect the temper. Instead of maintaining continuous grinding contact with the work, I subject the work intermittently to frequently repeated grinding actions and in the interval between these actions I flood the work with lubricant which is forced into the recesses 13 of the wheel and is forcibly carried through the thread of the work by the rotation of the wheel.

This application of lubricant has a direct action in cooling the metal and in removing all waste or dust from the cut and also reduces the heating effect of the wheel by thoroughly lubricating the surfaces to be ground. The passage of the edge of ,the wheel into and through the end of the pipe 15 also has an important effect in forcing the lubricant into the recess 13 and in fillin the pores or openings of the wheel with In ricant, at the same time removing any dust or waste therefrom.

This arrangement of mechanism and method of procedure not only enables me to prevent softening of the metal during the grindin operation, but also largely increases the pro uction as the grindin speed may be increased without heating t e work. It

' is,also found that a wheel will ,cut much faster and freer when provided with the openings 13 as shown in Fig. 1. Each sepaf t e rate grinding portion 0 wheel apparently makes a fresh cut as it passes through the work and the combined results of these numerous fresh cuts is found to be substantially greater than the results which would be obtained by a wheel having a continuous contact with the work.

It may also be noted that the recessed edge of the wheel has a certain fan effect which also tends to cool the wheel and work. Different kinds of oilor other lubricant may be used with my improved mechanism but I have found that for high 5 eed steel the best results are obtained by t e use of a very high grade'oil and particularly with sperm oil.

\Vhile I have shown m invention as particularly applied to the production of ground taps, important advantages thereof may be utilized in the production of continuous ground screw threads and other similar articles and such use of my invention is to be considered within the scope of my protection.

Having thus described my improved method or process of producing ground threads, it will be evident that changes and modifications can be made therein by those skilled in the art within the spirit and scope of my invention as set forth in the claims, and 1 do not wish to be otherwise limited to the details herein disclosed, but what I do claim is 1. The method of rinding screw threads in substantially cylint lrical work which consists in subjecting the work to the intermittent action of a series of grinding elements spaced apart to entirely discontinue grinding action bctween contacts with said elements and to permit momentary cooling of the work between such grinding contacts, and in forcing a lubricantagainst' the work in line with the thread and into the pores and recesses of the wheel to, remove the waste and cool the work between said intermitfent grinding actions.

2. The method of grinding screw threads in substantially cylindrical work which consists in subjecting the work tothe intermittent action of a grinding wheel having spaced recesses extendin transversely entirely across its cuttin e ge, and in forcing an a) said recesses as they approach the work, whereby the' lubricant is forcibly carried into the thread being formed and effectively cools the work and clears the thread and wheel of dust and waste.

In testimony whereof I have hereunto affixed my signature.

, JOHN BATH.

undant supply 0 liquid lubricant into 

